1. Field of the Invention
The invention relates to a connecting rod for an internal combustion engine and to an internal combustion engine.
2. Description of the Related Art
DE 10 2010 016 037 A1 and FIG. 1 herein show a connecting rod of an internal combustion engine that has an adjustable compression ratio. The connecting rod 10 has a big end bearing eye 11 for attaching the connecting rod 10 to a crankshaft (not shown in FIG. 1) and a small end bearing eye 12 for attaching the connecting rod 10 to a cylinder piston (not shown in FIG. 1) of the internal combustion engine. The connecting rod 10 is used with an eccentric adjusting device 13 that has an eccentric (not shown in FIG. 1), an eccentric lever 14 and eccentric rods 15, 16. The eccentric lever 14 has a bore arranged eccentrically with respect to a center 17 of the small end bearing eye 12 and has a center 18. The bore in the eccentric lever 14 accommodates the eccentric and a bore in the eccentric accommodates a piston pin. The eccentric adjusting device 13 is used to adjust an effective connecting rod length left, which is the distance of the center 18 of the bore in the eccentric lever 14 from a center 19 of the big end bearing eye 11. The eccentric rods 15, 16 can be moved to turn the eccentric body 14 and hence to change the effective connecting rod length left. Each eccentric rod 15, 16 is assigned a piston 20, 21 that is guided movably in a hydraulic chamber 22, 23. A hydraulic pressure prevails in the hydraulic chambers 22, 23 and acts on the pistons 20, 21 assigned to the eccentric rods 15, 16. Thus, movement of the eccentric rods 15, 16 is possible or not possible, depending on the oil quantity in the hydraulic chambers.
The adjustment of the eccentric adjusting device 13 is initiated by the action of inertia forces and load forces of the internal combustion engine that act on the eccentric adjusting device 13 during an operating cycle of the internal combustion engine. The directions of the forces acting on the eccentric adjusting device 13 change continuously during an operating cycle. The adjusting movement is assisted by the pistons 20, 21 acted upon by hydraulic oil, and the pistons 20, 21 act on the eccentric rods 15, 16 to prevent return of the eccentric adjusting device 13 due to varying directions of force of the forces acting on the eccentric adjusting device 13. The eccentric rods 15, 16 are attached to the eccentric body 14 on both sides. The hydraulic chambers 22 and 23 in which the pistons 20, 21 are guided can be supplied with hydraulic oil from the big end bearing eye 11 via hydraulic oil lines 24 and 25. Check valves 26 and 27 prevent the hydraulic oil from flowing back out of the hydraulic chambers 23 and 24 into the hydraulic lines 24 and 25. A changeover valve 29 is accommodated in a bore 28 in the connecting rod 10, and the switching position of the changeover valve 29 determines which of the hydraulic chambers 22 and 23 is filled with hydraulic oil and which of the hydraulic chambers 22 and 23 is emptied, thereby determining the adjusting direction or turning direction of the eccentric adjusting device 13. The hydraulic chambers 22 and 23 are in contact with the bore 28 that accommodates the changeover valve 29 via fluid lines 30 and 31, respectively. An actuating means 32, a spring device 33 and a control piston 34 of the changeover valve 29 are shown schematically in FIG. 1, and the operation of these components of the changeover valve 29 is known from DE 10 2010 016 037 A1.
As explained above, the hydraulic oil is fed from the big end bearing eye 11 to the hydraulic chambers 22, 23 via hydraulic lines 24 and 25. The connecting rod 10 engages on the crankshaft (not shown in FIG. 1) via the big end bearing eye 11 so that a connecting rod bearing shell 35 is arranged between a crankshaft bearing journal of the crankshaft and the big end bearing eye.
As explained above, a first end 36, 37 of each respective eccentric rod 15, 16 engages on the eccentric lever 14, while a second end 38, 39 of each respective eccentric rod 15 or 16 engages on a piston 20 or 21 that is guided respectively in the hydraulic chambers 22, 23 of the connecting rod 10, as shown in FIG. 1. Connecting pins are used to ensure hinge-type articulated attachment of the ends 36-39 of the eccentric rods 15, 16 to the eccentric lever 14 and the pistons 20, 21. However, the connecting pins require a high outlay on components and on manufacture. An improved attachment of the second ends 38, 39 of the eccentric rods 15, 16 to the pistons 20, 21 that are guided in the hydraulic chambers 22, 23 would be well received commercially.
It is the object of the invention to provide a novel internal combustion engine and a novel connecting rod.